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Marco Tahtaras · 05-02-2011, 10:06 AM

I started to write this yesterday morning but was pulled away. Since then some have thought through the concept.

What Chris did was increase the leverage to the fronts which were technically under leveraged compared to later cars when Ford finally understood the reality of front versus rear needs. Yes, this does slow the actuation of the front brakes. That is normal and unavoidable. Look at the ratios of any block and tackle. The lift capacity is not determined by the size of the cable or rope (although it must be suitably sized), but the the capacity is determined by the ratio or number of wraps of the cable. The more wraps, the slower it lifts but the more it lifts with the same applied force.

Everyone assumes the Model A front brakes actuate or engage at the same rate as the rears. This is not the case. The topic came up about ten years ago regarding an article written suggesting the brakes could be adjusted 50-50 or 60-40 front-rear. I explained at that time it was simply a fallacy. In doing so you are simply reducing the function of the rear brakes and FORCING the much stiffer (less leverage) front brakes to do more of the work. Think of it this way, shortening the front brake rods to make the front brakes come on earlier is the same as lengthening the rear rods to come on later (reducing rear brake function) except the latter lowers the functional height of the brake pedal. I further explained that to even equalize the braking force at the drum (front to rear) you must actually equalize the leverage. This essentially also means making the brakes actuate at the same rate.

Now it's important to note that the simpler linkage of the rear brakes DOES provide a slight mechanical advantage due to efficiency but not nearly to the extent that the the added leverage (and slower actuation) does. Adding leverage to the fronts will similarly slow the actuation which can then be adjusted to engage at the proper time. Wear will not cause any future adjustment issues assuming the modification is not too extreme.

05-02-2011, 10:06 AM	#23
Marco Tahtaras Senior Member Join Date: May 2010 Posts: 3,099	Re: Mechanical brakes, what i did I started to write this yesterday morning but was pulled away. Since then some have thought through the concept. What Chris did was increase the leverage to the fronts which were technically under leveraged compared to later cars when Ford finally understood the reality of front versus rear needs. Yes, this does slow the actuation of the front brakes. That is normal and unavoidable. Look at the ratios of any block and tackle. The lift capacity is not determined by the size of the cable or rope (although it must be suitably sized), but the the capacity is determined by the ratio or number of wraps of the cable. The more wraps, the slower it lifts but the more it lifts with the same applied force. Everyone assumes the Model A front brakes actuate or engage at the same rate as the rears. This is not the case. The topic came up about ten years ago regarding an article written suggesting the brakes could be adjusted 50-50 or 60-40 front-rear. I explained at that time it was simply a fallacy. In doing so you are simply reducing the function of the rear brakes and FORCING the much stiffer (less leverage) front brakes to do more of the work. Think of it this way, shortening the front brake rods to make the front brakes come on earlier is the same as lengthening the rear rods to come on later (reducing rear brake function) except the latter lowers the functional height of the brake pedal. I further explained that to even equalize the braking force at the drum (front to rear) you must actually equalize the leverage. This essentially also means making the brakes actuate at the same rate. Now it's important to note that the simpler linkage of the rear brakes DOES provide a slight mechanical advantage due to efficiency but not nearly to the extent that the the added leverage (and slower actuation) does. Adding leverage to the fronts will similarly slow the actuation which can then be adjusted to engage at the proper time. Wear will not cause any future adjustment issues assuming the modification is not too extreme. __________________ http://www.abarnyard.com/